2 Chapter 6 • organising elements Organising elements

2000 years ago
The ancient Greeks thought
that everything was made
of four ‘elements’ mixed
together in different ratios.
1789
Air
Hot
Wet
Fire
Water
Antoine Lavoisier, a French nobleman, made a
detailed list of the substances that he believed to be
elements. Assisted by his wife, his list contained
33 elements grouped according to metals and nonmetals.
Lavoisier’s list also included some substances
that we now know to be compounds, but he lacked
the understanding and equipment, or technology, to
identify them as such.
Dry
Cold
Earth
1820s
1829
1661 ce
The Irish-born chemist
Robert Boyle suggested that
an element was a substance
that cannot be broken down
into a simpler substance in
a chemical reaction. Many
historians and scientists
see this as the beginning of
modern chemistry.
Jakob Berzelius was
a Swedish chemist who
replaced the geometric
patterns used as chemical
symbols with letters that
were an abbreviation of the
element’s name. Berzelius chose to use English names
for most elements, with just a few retaining their
Latin names. In addition, Berzelius used the weight
of hydrogen to develop a coherent system of atomic
weights. Because hydrogen was the lightest element,
it was given a value of 1, with all remaining elements
believed to have a whole number above 1.
Importantly, Berzelius is known for combining all
current knowledge of his time into a single system.
This enabled chemists across the world to share
their thoughts and systems in a unified approach.
As more elements were identified, more and more chemists
studied them and their properties. In Germany, Johann
Dobereiner was aware of 40 elements. He noted that some
groups of three elements had similar properties and named
these groups triads. These groupings were instrumental in
identifying patterns of behaviour, which assisted with more
accurate speculation regarding atomic structures.
UNCORRECTED PAGE PROOFS
Unit 6.1 • Why do we organise elements? 5
CAS_SB10_TXT_06_1pp.indd 5
11/11/11 4:58 PM